Glass reinforced or non-reinforced thermoplastic polyesters and polyamides are used for the production of electronic parts such as connectors, frames, moving parts, transformers, micro motors, amongst others. In most of these applications, flame retardancy is needed and is usually provided by flame retardant systems based on a combination of brominated flame retardants with antimony trioxide as synergist. But this type of flame retardant system has a limitation, because antimony trioxide, being a very efficient synergist, tends to significantly increase the smoke yield, which impairs visibility and creates problems for evacuation of people in the case of fire. Furthermore, antimony trioxide has a very high bulk density which increases the specific gravity of molded parts. This is especially undesirable in transportation and aviation. Even furthermore, antimony trioxide has significantly increased in price in recent years. Even furthermore some recently introduced ecolabels require elimination of antimony trioxide from thermoplastic parts.
Although there is a clear need for low antimony trioxide or antimony trioxide free flame retardant plastics, such usually requires a significant increase in the loading of brominated flame retardant.